Exit with non-zero if Whiskey exists with non-zero.
Improve the assert, make sure the output actually contains coverage data.
Merge pull request #63 from cloudkick/improve_coverage_test_asserts

Improve coverage test asserts
Add rewire to TestFile.runTests() so when coverage is running, the test module has the covered resources in lib/ injected into its scope.

Remove the lib-cov in NODE_PATH requirement as it isn't needed with rewire